Repair tack for bodily tissue

ABSTRACT

An apparatus for repairing in vivo torn cartilaginous or other bodily tissue, particularly torn meniscus tissue during arthroscopic surgery, employs a repair tack of biodegradable material chosen to have a degradation time in excess of the required healing time for the tissue. The repair tack has a shaft portion with a longitudinal bore and a grip portion adapted for releasable engagement by a hollow applicator. In one embodiment the grip portion of the tack is a cross bar, at the proximal end of the shaft, which fits into an open-sided slot at the forward end of the applicator.

This application is a continuation of application Ser No. 06/865,184filed May 20, 1986, now abandoned.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to an apparatus for repairing bodilytissue in vivo and has particular utilization in repairing a meniscaltear during arthroscopic surgery of the knee.

2. Discussion of the Prior Art

Although the following description is directed specifically to repairingmeniscus tissue in vivo in a human knee, it should be understood thatthe principles of the present invention are applicable to the repair ofany bodily tissue, such as cartilage, bone, skin and ligaments, in an invivo surgical procedure.

The knee is a hinge joint which permits a limited amount of rotation.The opposing curvature of the articulating surfaces of the femur andtibia are equalized, to a certain degree, by the menisci, thewedge-shaped fibrocartilaginous structures located on the periphery ofthe articular surface. The menisci are mobile buffers functioning toinhibit displacement of the joint and to distribute the force exerted bythe femur over a larger area of the tibia. Possible causes of damage orinjury to the menisci are multiple. Damage or tear of a meniscus usuallyoccurs when the weight-bearing joint is subjected to a combinedflexion-rotation or extension-rotation motion. The elastic and fibrousstructure of the menisci, the rigid fixation of the anterior andposterior attachments, and their connections with the joint capsule,cause the menisci to return to their normal positions at the peripheryof the joint if there is displacement. Disturbance of the normalmechanism of the joint and interference with mobility of the menisci canexceed their elasticity and cause tears of the cartilaginous substance.This appears to occur most frequently when a meniscus that has beendisplaced into the joint is caught between the femoral and tibialcondyles as the result of a sudden change of movement.

Treatment for torn menisci has changed considerably over the years. Atone time it was advocated that a peripherally detached meniscus beremoved, even though the tissue was not damaged. The rationale was thatexcision of the meniscus prevents meniscal re-injury in a joint in whichthe mechanics may have been disturbed. In many cases a completemeniscectomy (i.e., total removal of the meniscus) was performed.Results from a complete meniscectomy ultimately showed degenerativearthritis, instability and changes in the transmission of loads in theknee. Because of these complications a partial meniscectomy became analternative to a complete meniscectomy. Recently, there has been astrong movement to save as much of the meniscus as possible, leading tothe development of techniques for meniscal suturing. Animal studies havebeen performed to demonstrate the safety and efficiency for thisprocedure.

An arthrotomy, or open technique, requires large incisions to gainaccess to the joint. Utilizing the open technique for meniscal suturingrepair provided the opportunity of returning the knee to its priorpre-injury level of performance; however, the resulting large incisionsrequire longer periods of immobilization and consequently longer periodsof rehabilitation and recovery. Recent advances in instrumentation havemade it possible to repair some meniscal lesions under arthroscopicvisualization. Generally, this instrumentation is for inserting andreceiving the suture as it passes through the meniscus. Typically,suture is passed through the meniscal rim and body of the meniscus,guided by special cannulas through the knee. The suture is then tiedposterior to the knee and placed subcutaneously. Most of theseprocedures are performed using a larger (i.e., four to eightcentimeters) incision than the standard portals used in arthroscopy.Depending upon the meniscus to be repaired, the incision is placed onthe medial or lateral side of the knee; however, because of the longneedles generally employed in meniscal repair, extreme caution must beobserved during this procedure in order to avoid the possibility of theneedle penetrating the popliteal artery or posterior tibial nerve andcatching the fat pad during passage of the needle into and out of theknee joint. A spoon-shaped instrument is generally employed to act as aneedle shield or guard for the popliteal structures. Nevertheless, therehave been reported instances of injury to these vital areas withconsequential damage to arteries and nerve palsy in the limb. Surgicaltechniques are being perfected, as are improvements to instrumentation,by various groups in order to minimize these risks and to decrease theprocedural time.

It is known to use certain types of metal staples in conjunction withsurgery for repairing bone tissue. The legs or shafts of the staple havea series of barbs which hold the staple and surrounding base tissue inplace during the healing process. Another known device serving a similarfunction is the Smillie nail which is a single shaft device employed forsecuring bone tissue parts in place during the healing process. Thesestaple and nail devices are effective for holding the bone tissuetogether during healing; however, they require a second surgicalprocedure in order to remove the device after the tissue has healed.

OBJECTS AND SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide anapparatus for repairing bodily tissue in vivo requiring only a singlesurgical procedure and a small incision.

It is another object of the present invention to provide an apparatusfor healing torn or severed tissue, particularly meniscus tissue, usinga safer surgical procedure than is currently employed.

A further object of the present invention is to provide an apparatus forhealing torn or severed bodily tissue with a single surgical procedurerequiring far less time than the procedure currently employed.

In accordance with the present invention a repair tack is designed forsurgical utilization, particularly in arthroscopic surgery, to repair atorn meniscus, the tack being generally T-shaped with a hollow stem.Along the outer surface of the stem there are a plurality of barbs. Anapplicator for the repair tack includes a tack holder having a slot forreceiving the cross bar of the T-shaped tack and further includes aneedle passing through an axial opening in the applicator and throughthe axial bore in the stem of the tack. With the tack supported in theslot and the needle passing through the stem, the applicator and thetack can be inserted into the joint cavity through a portal in the skinor through an insertion cannula. The sharpened point of the needle isplaced in contact with the torn meniscus portions (or other severedtissue) and force is applied to the holder and needle to cause theneedle and tack to penetrate those meniscus portions to a desired depth.The point of the needle is then withdrawn into the axial opening of theapplicator and the cross bar of the tack is displaced from the slotleaving the tack firmly secured in the meniscus. The tack is made from abiodegradable polymer or copolymer selected in accordance with desireddegradation time and anticipated time for healing the torn meniscus.

The tack performs a function similar to that of biodegradable suturepresently employed in meniscal and other surgical repair. It is saferthan utilizing suture because it penetrates only the meniscus and doesnot enter the popliteal space. The risk in reaching and possiblydamaging the vital areas in the posterior section of the knee is greatlyreduced. The tack device holds the torn meniscal sections in appositionwhile the tissue regenerates and healing is effected. In addition, thetime required for placement of the tack device is much shorter than thatrequired to place the suture. Consequently, the total procedural time isshortened, thereby decreasing the time during which a tourniquet must beutilized to restrict blood flow to the limb. Thus, reduced risk ofpossible damage to the vital area in the back of the knee, and reducedtourniquet time, are primary advantages of the tack device.

The repair tack is formed from an absorbable polymer or copolymer,preferably derived from glycolic and lactic acids. It is a syntheticpolyester chemically similar to other commercially availableglycolide/lactide copolymers. In vivo, glycolide and lactide degrade andabsorb by hydrolysis to lactic acid and glycolic acid which are thenmetabolized by the body. The combination of glycolide and lactide hasbeen used for many years in suturing material.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and still further objects, features and advantages of thepresent invention will become apparent upon consideration of thefollowing detailed description of a specific embodiment thereof,especially when taken in conjunction with the accompanying drawingswherein like reference numerals in the various figures are utilized todesignate like components, and wherein:

FIG. 1 is a view in perspective of a repair tack, applicator andinsertion needle of the present invention;

FIG. 2 is a detailed side view in elevation of the forward end of theapparatus of FIG. 1;

FIG. 3 is a top view in plan and partial section of the tack device ofthe apparatus of FIG. 1;

FIG. 4 is an end view in elevation of the tack device of FIG. 3;

FIG. 5 is a view in perspective of an alternative embodiment of the tackdevice employed with the apparatus of FIG. 1;

FIG. 6 is a view in perspective of still another embodiment of the tackdevice of the present invention;

FIG. 7 is a view in section taken along lines 6--6 of FIG. 6; and

FIG. 8 is a view in perspective of a further embodiment of the tackdevice of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring specifically to FIGS. 1-4 of the accompanying drawings, apreferred embodiment of the present invention takes the form of a repairtack 10 for deployment in torn cartilage or other bodily tissue, invivo, by means of an applicator 20 and needle 30. The repair tack 10 ispreferably fabricated as an integrally molded unit from suitable rigidor semi-rigid biodegradable plastic material chosen in accordance withconsiderations described hereinbelow. It should also be noted that thetack may be formed by means of any suitable process, such as machining.Proximal and distal ends of the tack are designated by referencenumerals 11 and 12, respectively, and are joined by a bore 13 extendingaxially (i.e., longitudinally) through the entire length of the tack 10.Most of that length is occupied by a shaft portion 14 extendingrearwardly from distal end 12 to join a cross bar grip portion 15disposed at proximal end 11. Grip portion 15, in the embodiment of FIGS.1-4, takes the form of a generally rectangular parallelepiped withrounded corners and having its longest dimension extending transverselywith respect to the axis of shaft 14 and internal bore 13. As is clearlyillustrated in FIG. 3, bore 13 extends perpendicularly through the crossbar grip portion 15 and axially through shaft portion 14.

The shaft portion 14 is substantially cylindrical, with bore 13 disposedcoaxially therein, and includes a plurality of barb members 16 disposedin axial sequence along its periphery. In the preferred embodiment thebarb members 16 are frusto-conical in configuration, widening indiameter in a direction from distal end 12 toward proximal end 11.

The distal barb tapers to terminate at a sharp circular edge at thedistal end 12 of the shaft.

The resulting tapered surface 18 of the barb members 16 facilitatespassage of the shaft portion 11 of tack member 10 through cartilaginousor other tissue when the tack is moved forwardly (i.e., in a directionalong the axes of shaft portion 14 and bore 13 from proximal end 11toward distal end 12). The rearward facing surface 17 of each barbmember 16 intersects the large diameter end of tapered surface 18 andincludes an annular section disposed in a plane oriented substantiallyperpendicular to the axes of bore 13 and shaft portion 14. Thisperpendicular orientation is not crucial for the present invention;rather, what is important is that surface 17 be oriented to precluderearward movement and resulting inadvertent removal of the tack member10 from cartilaginous or other tissue into which the tack member hasbeen deployed. In this regard, it is important that surface 17 not betapered to any significant degree in the opposite direction to the taperof surface 18. In the preferred embodiment of the invention there arethree barb members 16 disposed in successive axial adjacency with themost remote barb member having its narrow diameter end terminating atdistal end 12. Approximately one-third of the length of shaft portion 14remains between the rearmost barb member 16 and cross-bar grip portion15 and has a smooth cylindrical configuration. As few as one and morethan three barb members may be provided within the scope of the presentinvention, so long as the barb member or members provide sufficientresistance to rearward movement of the shaft portion through thecartilaginous tissue.

Applicator 20 is an elongated hollow cylindrical member having a forwardend 21 adapted for attachment to tack member 10 and a rearward end 22from which deployment of the tack member is controlled. The hollowinterior of applicator 20 may take the form of an axial bore suitablefor receiving needle 30 in axially slidable engagement. Forward end 21of applicator 20, when viewed from the side, has a generally J-shapedconfiguration to define a slot 23 for receiving the cross-bar gripportion 15 of tack member 10. Specifically, slot 23 has an interiorsurface 24 contoured to match the contour of grip portion 15 and is openalong one side to permit easy insertion and removal of the grip portion.A forward lip 25 extends across the slot 23 terminating the short leg ofthe J-configuration and serves to restrain the grip portion 15 of tackmember 10, when it is in slot 23, against axial movement (i.e.,longitudinally of applicator 20 and tack member 10) and against twistingor rotation about any axis extending vertically (as viewed in FIG. 2). Acut-out portion 26 in lip 25 receives and supports the rearmost end ofthe shaft portion 14 of the tack member and, along with needle 30,precludes movement of grip portion 15 along its axis transversely ofshaft portion 14.

Needle 30 has a sharp end 31 and a rearward end 32 and is sufficientlylong to extend entirely through applicator 20 and tack member 10 suchthat pointed end 31 extends forwardly of the distal end 12 of the tackmember. The bores defined in applicator 20 and tack member 10 are sizedto permit slidable movement of the needle within these members. Rearwardend 32 of needle 30 includes an enlarged handle part which can begrasped between a surgeon's thumb and forefinger so that the needle canbe pushed forwardly into and pulled rearwardly from cartilaginoustissue. The needle is preferably made from stainless steel and issecured, at its rearward end, to a threaded male connector adapted toengage a threaded female connector 27 at the rearward end of applicator20. The applicator is preferably made from a suitably machined or moldedmetal material.

Tack member 10 is made from a biodegradable polymer or copolymer of atype selected in accordance with the desired degradation time. Thattime, in turn, depends upon the anticipated healing time for thecartilaginous or other tissue which is the subject of the surgicalprocedure. Known biodegradable polymers and copolymers range indegradation time from about three months for polyglycolide to aboutforty-eight months for polyglutmic-co-leucine. A common biodegradablepolymer used in absorbable sutures and the like is poly(L-lactide) whichhas a degradation time of about twelve to eighteen months.

As discussed briefly above, the actual material used for tack member 10is preferably an absorbable copolymer derived from glycolic and lacticacids, such as a synthetic polyester chemically similar to othercommercial available glycolide and lactide copolymers. Glycolide andlactide, in vivo, degrade and absorb by hydrolysis into lactic acid andglycolic acid which are then metabolized by the body.

The table set forth below lists polymers (and copolymers and terpolymersthereof) which are useful for the biodegradable material employed forthe tack member 10 of the present invention. These polymers are allbiodegradable into water-soluble non-toxic materials which can beeliminated by the body. All are well known for use in humans and theirsafety has bee demonstrated and approved by the U.S. Food and DrugAdministration. Although these polymers are normally linear, crosslinked resins can be prepared from these materials by those skilled inthe art.

                  TABLE                                                           ______________________________________                                        Polymer                                                                       ______________________________________                                        Polycaprolactone                                                              Poly(L-lactide)                                                               Poly(DL-lactide)                                                              Polyglycolide                                                                 95:5 Poly(DL-lactide-co-glycolide)                                            90:10 Poly(DL-lactide-co-glycolide)                                           85:15 Poly(DL-lactide-co-glycolide)                                           75:25 Poly(DL-lactide-co-glycolide)                                           50:50 Poly(DL-lactide-co-glycolide)                                           90:10 Poly(DL-lactide-co-caprolactone)                                        75:25 Poly(DL-lactide-co-caprolactone)                                        50:50 Poly(DL-lactide-co-caprolactone)                                        Polydioxanone                                                                 Polyesteramides                                                               Copolyoxalates                                                                Polycarbonates                                                                Poly(glutamic-co-leucine)                                                     ______________________________________                                    

The repair tack 10 illustrated in the accompanying drawings is primarilyintended for use in arthroscopic surgery for the repair of torn meniscustissue; however, it also has utilization for repairing other bodilytissue. The apparatus illustrated in FIG. 1 is assembled, prior toinsertion into the body joint, by placing the cross bar portion 15 intoslot 23 at the forward end of applicator 20. Needle 30 is then slidablypassed through the hollow applicator and bore 13 in tack member 10, andthreaded connectors 27 and 32 are tightened. With the tack member firmlysupported in slot 23 and by needle 30, the device may be inserted intothe joint cavity where the meniscus repair is to take place through asuitable portal in the skin or through an insertion cannula.

In order to apply the tack to the torn cartilaginous tissue, thesharpened point 31 of the needle is placed into contact with the tissueand force is applied to the applicator and needle 30 (locked together bythe above-described threaded engagement) to cause the needle and tack topenetrate the torn meniscus portions to the desired depth. Theconnectors 27 and 32 are disengaged and the sharpened point 31 of theneedle is then withdrawn from the tack member 10 into the applicator 20.Cross bar grip portion 15 may then be removed from slot 23 by rotatingthe forward end of applicator 20 downwardly (i.e., downwardly as viewedin FIG. 2), transversely of the axis of bore 13. Applicator 20 may thenbe withdrawn away from the tack, leaving the tack 10 firmly securedwithin the torn meniscus portions in a position to retain the tornportions in close proximity. As noted above, the tack dissolves over aperiod of time sufficient to permit healing of the torn meniscus tissue.

As illustrated in FIGS. 5, 6, 7 and 8, the barb members on the tack neednot be limited to a frusto-conical configuration, nor must the gripportion be cylindrical. Any barb and grip portion configurationconsistent with the functions described herein may be employed. Thus,the tack member illustrated in FIG. 5 is provided with barb members 36having a truncated pyramidal configuration with a substantially squareor other rectangular transverse cross section. The embodiment of FIGS. 6and 7 includes barb members 46 which are truncated pyramids having atriangular transverse cross section. In both of these embodiments, thegrip 35 takes the form of a rectangular parallelepiped. In theembodiment of FIG. 8 the "barbs" are actually a continuous helical barb50 extending about the shaft periphery for a portion of the shaftlength.

As noted above, the tack member 10 is ideally suited for holding tornmeniscus tissue in place while the tissue heals. By way of example only,a suitable set of dimensions for tack member 10 of FIGS. 1-3 would be asfollows: the overall length from proximal end 11 to distal end 12: 0.345inch; the axial length of the distal barb member: 0.075 inch; the axiallength of the other barb members: 0.06 inch; the diameter of each barbmember at its widest end: 0.065 inch; the diameter of bore 13: 0.025inch; overall length of cross bar grip portion 15 in the dimensionextending transversely of bore 13 and radially symmetrically thereabout:0.175 inch; thickness of cross bar grip portion 15 parallel to the axisof bore 13: 0.025 inch; and angle of surface 18 relative to axis of bore13: 14°. It is to be understood, of course, that variations from thesedimensions are possible for different utilizations of tack member 10.

The positioning of bore 13 of tack member 10 along the axial center lineof the tack member is advantageous in that it permits the insertionneedle to stabilize the tack and provide a means for penetrating thetissue.

From the foregoing description it will be appreciated that the inventionmakes available a novel method and apparatus for healing torncartilaginous tissue, in vivo, in a manner which requires a singlesurgical procedure utilizing a minimal amount of time and a relativelysmall incision.

Having described the preferred embodiment of a new and improved repairtack for cartilaginous tissue and in vivo method of deploying same inaccordance with the present invention, it is believed that othermodifications, variations and changes will be suggested to those skilledin the art in view of the teachings set forth herein. It is therefore tobe understood that all such variations, modifications and changes arebelieved to fall within the scope of the present invention as defined bythe appended claims.

We claim:
 1. A tack for holding together severed or torn segments of themeniscus to permit healing in vivo comprisinga shaft having a proximalflange-like end, a distal end and a substantially cylindrical boreextending longitudinally from said proximal end to said distal end toallow a needle to pass freely entirely through said shaft to extend fromsaid distal end for penetration in the meniscus segments; and aplurality of tapered barbs disposed longitudinally in axial sequencealong at least one-half of the length of said shaft, said barbs havingsubstantially equal points of maximum width to be imbedded in themeniscus segments and including a distal barb tapering to terminate at asharp circular edge at said distal end of said shaft, said sharpcircular edge having a diameter substantially the same as said bore tofacilitate penetration and imbedding of said barbs in the meniscussegments, the entirety of said tack being made of a biodegradablematerial having a degradation time selected to be at least as long asthe required healing time for the meniscus.
 2. The tack according toclaim 1 wherein said barbs have rear surfaces facing said proximal endand disposed substantially perpendicular to the longitudinal dimensionof said shaft.
 3. The tack according to claim 1 wherein said barbs eachhave a frusto-conical configuration.
 4. The tack according to claim 1wherein said barbs each have a truncated pyramidal configuration.
 5. Thetack according to claim 4 wherein each of said barbs has a generallytriangular transverse cross section.
 6. The tack according to claim 4wherein each of said barbs has a generally rectangular transverse crosssection.
 7. The tack according to claim 1 wherein the tack in itsentirety is an integrally-molded plastic unit.
 8. The tack according toclaim 1 wherein said barbs are formed of a continuous helical barbextending about said shaft over a portion of the length of said shaft.9. A tack according to claim 1 wherein said distal barb has an axiallength greater than the axial length of the other barbs.